Pump-Less Cooling

ABSTRACT

A method of cooling that accelerates a compressible working fluid without the use of a pump. The method accelerates the fluid to a velocity equal to or greater than the speed of sound in the compressible fluid selected to be used in the method. The fluid is accelerated to a supersonic velocity in a rotating evaporator tube. A phase change of the fluid due to a pressure differential may be utilized to transfer heat from an element to be cooled.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is related to U.S. patent application Ser. No. 12/732,171, filed Mar. 25, 2010, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to cooling systems. The present invention more specifically relates to a supersonic cooling without the need for a conventional mechanical pump.

2. Description of the Related Art

A vapor compression system as known in the art generally includes a compressor, a condenser, and an evaporator. These systems also include an expansion device. In a prior art vapor compression system, a gas is compressed whereby the temperature of that gas is increased beyond that of the ambient temperature. The compressed gas is then run through a condenser and turned into a liquid. The condensed and liquefied gas is then taken through an expansion device, which drops the pressure and the corresponding temperature. The resulting refrigerant is then boiled in an evaporator. This vapor compression cycle is generally known to those of skill in the art.

FIG. 1 illustrates a vapor compression system 100 such as might be found in the prior art. In the prior art vapor compression system 100 of FIG. 1, compressor 110 compresses the gas to (approximately) 238 pounds per square inch (PSI) and a temperature of 190° F. Condenser 120 then liquefies the heated and compressed gas to (approximately) 220 PSI and 117° F. The gas that was liquefied by the condenser 120 is then passed through the expansion valve 130 of FIG. 1. By passing the liquefied gas through expansion valve 130, the pressure is dropped to (approximately) 20 PSI. A corresponding drop in temperature accompanies the drop in pressure, which is reflected as a temperature drop to (approximately) 34° F. in FIG. 1. The refrigerant that results from dropping the pressure and temperature at the expansion valve 130 is boiled at evaporator 140. Through boiling of the refrigerant by evaporator 140, a low temperature vapor results, which is illustrated in FIG. 1 as having (approximately) a temperature of 39° F. and a corresponding pressure of 20 PSI.

The cycle related to the system 100 of FIG. 1 is sometimes referred to as the vapor compression cycle. Such a cycle generally results in a coefficient of performance (COP) between 2.4 and 3.5. The coefficient of performance, as reflected in FIG. 1, is the evaporator cooling power or capacity divided by compressor power. It should be noted that the temperature and pressure references that are reflected in FIG. 1 are exemplary and illustrative.

Such a system 100, however, operates at an efficiency rate (i.e., COP) that is far below that of system potential. To compress gas in a conventional vapor compression system 100 like that illustrated in FIG. 1 typically takes 1.75-2.5 kilowatts for every 5 kilowatts of cooling power generated. This exchange rate is less than optimal and directly correlates to the rise in pressure times the volumetric flow rate. Degraded performance is similarly and ultimately related to performance (or lack thereof) by the compressor 110. For example, a prior art compression system 100 as illustrated in FIG. 1 that requires 1.75-2.5 kilowatts to generate 5 kilowatts of cooling power operates at a coefficient of performance (COP) of less than 3.

Haloalkane refrigerants such as tetrafluoroethane (CH₂FCF₃) are inert gases that are commonly used as high-temperature refrigerants in refrigerators and automobile air conditioners. Haloalkane refrigerants have also been used to cool over-clocked computers. These inert, refrigerant gases are more commonly referred to as R-134 gases. The volume of an R-134 gas can be 600-1000 times greater than the corresponding liquid.

There is a need in the art for an improved cooling system that more fully recognizes system potential and overcomes technical barriers related to compressor performance. There is a further need for a cooling system that operates without the use of a conventional mechanical pump.

SUMMARY OF THE CLAIMED INVENTION

A first claimed embodiment of the present invention is for a cooling method. Through the method disclosed herein, at least a portion of a fluid pathway is rotated. A compressible fluid contained in the fluid pathway is accelerated to a velocity greater than or equal to the speed of sound in the compressible (multi-phase) fluid. The increased velocity of the fluid establishes a low pressure region in the pathway, and forms a compression wave in the compressible fluid as the compressible fluid passes from a high pressure region to the low pressure region. The pressure change and an accompanying phase change occurs in an evaporator tube. Heat is introduced into the fluid pathway during the phase change of the compressible fluid so that the heat is removed from an element to be cooled.

A second claimed embodiment of the present invention is for a supersonic cooling system that includes an enclosure defining a fluid pathway. At least a portion of the fluid pathway rotates about an axis central to the enclosure. The rotatable portion of the fluid pathway includes one or more evaporator tubes. The system further includes a driving mechanism to provide a motive force to drive the rotatable portion of the fluid pathway. As the rotatable portion spins, fluid in the evaporator tubes flows in the critical flow regime to generate a compression wave. The compression wave helps to cause a pressure change in the fluid so that the temperature of the fluid is reduced. Heat is exchanged with the fluid in the fluid pathway to remove heat from an element to be cooled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior art vapor compression cycle.

FIG. 2 illustrates an exemplary cooling system.

FIG. 3 is an exploded view of the cooling system illustrated in FIG. 2.

FIG. 4 illustrates a cross sectional view of a nozzle utilized in the cooling system illustrated in FIG. 2.

FIG. 5 illustrates a method of supersonic cooling.

DETAILED DESCRIPTION

Embodiments of the present invention implement a supersonic cooling method that increases efficiency as compared to prior art cooling systems. A system utilizing the present invention may be expected to operate at a COP of 10 or greater due to the elimination of hardware elements and due to the implementation of a supersonic cycle. The present invention does not require a compressor or a conventional mechanical pump to operate. Only an electric motor or some other driving mechanism to impart a rotating force is required.

FIG. 2 illustrates an exemplary cooling system 200. The cooling system 200 of FIG. 2 does not require the compression of a gas as otherwise occurs at compressor 110 in a prior art vapor compression system 100 like that shown in FIG. 1. The cooling system 200 of FIG. 2 operates by accelerating a working liquid, which may be water, in evaporator tubes 210. Because cooling system 200 utilizes liquid, the compression cooling system 200 does not require the use of a condenser 120 as does the prior art compression system 100 of FIG. 1. Compression cooling system 200 instead utilizes a rotating portion with the evaporator tubes 210 that generates a compression wave.

The evaporator tubes 210 of cooling system 200 operate in the critical flow regime of the working fluid, as is disclosed in U.S. patent application Ser. No. 12/732,171, the disclosure of which has been previously incorporated by reference. In this regime, the pressure of the fluid in the evaporator tubes 210 will remain almost constant and then ‘jump’ or ‘shock up’ to the ambient pressure.

Because cooling system 200 accelerates the working fluid through rotational movement, cooling system 200 does not require the use of a conventional mechanical pump as would a traditional prior art cooling system. The reduced amount of hardware required to operate the system 200—there is no need for a compressor or a conventional mechanical pump—and the implementation of a supersonic cooling cycle gives rise to a greatly improved coefficient of performance (COP) for the system 200.

The evaporator tubes 210 may be mounted in a rotating portion 220 of a system housing 230. An inlet end 205 of each of the evaporator tubes 210 is in fluid communication with a central throughway 310 as shown in FIG. 3. Outlet ends 215 of each of the evaporator tubes 210 may be in fluid communication with the rotating portion 220 of the housing 230.

The central throughway 310 may be in fluid communication with both the rotating portion 220 and a fixed portion 240 of the housing 230. The fixed portion 240 and the rotating portion 220 of the housing 230 may be coupled in fluid communication via an annular channel as well as via the central throughway 310. The annular channel is formed by the mating of an annular groove 320 shown in FIG. 3) in the upper surface of the rotating portion 220 with an annular groove 320 (shown in FIG. 3) in the lower surface of the fixed portion 240.

As the rotating portion 220 spins, the working fluid is introduced to the inlets 205 of the evaporator tubes 210. The motion of the rotating portion 220 accelerates the fluid as it travels through the evaporator tubes 210 outward to the circular perimeter of the rotating portion 220 of the housing 230. (The effects of the fluid flow through the evaporator tubes 210 are described in greater detail below.) After exiting the evaporator tubes 210, the working fluid flows through the annular channel into the fixed portion 240 of the housing 230. The fluid then travels from the fixed portion 240 through one or more hollow spokes 250 in the fixed portion 240, through the central throughway 310, and back to the inlets of the evaporator tubes 210.

The defined fluid pathway is a continuous loop when the rotating portion 220 of the housing 230 is spinning. The centrifugal force generated by the rotation of the rotating portion 220 accelerates the working fluid through the evaporator tubes 210. The working fluid flows through the rotating portion 220 into the fixed portion 240 via the annular groove 320. The acceleration of the working fluid in the evaporator tubes 210 creates suction. The suction draws the fluid through the spokes 250 and back to the central throughway 310. The working fluid flows to the lower end of the central throughway 310 where the fluid is again introduced to the inlets 205 of the evaporator tubes 210.

In the evaporator tubes 210, the fluid reaches the critical flow rate. The critical flow rate is the maximum flow rate that can be attained by a compressible fluid as that fluid passes from a high pressure region to a low pressure region (i.e., the critical flow regime). Critical flow occurs when the velocity of the fluid is greater than or equal to the speed of sound in the fluid. Operating in the critical flow regime allows for a compression wave to be established and utilized in the evaporator tubes 210. In critical flow, the pressure in the tube 210 will not be influenced by the exit pressure. As the fluid exits the evaporator tubes 210, the fluid ‘shocks up’ to the ambient conditions.

An interface plate 260 may be installed to assist in the exchange of heat from an element to be cooled 270. The interface plate 260 may be in thermal communication with the rotating portion 220 of the housing 230, either through direct contact or via a thermally conductive connector. The interface plate 260 may be a solid metal disc. The metal may be chosen to have a large heat transfer coefficient. Similarly, materials for the evaporator tubes 210 and for the housing 230 may be chosen based on their weight and heat conducting characteristics. Aluminum is one example of a material that may be chosen to construct the evaporator tubes 210 and the housing 230.

The interface plate 260 may be connected to the rotating portion 220 so that the interface plate 260 also rotates. A connection mechanism may be made by forming depressions 265 in the interface plate 260. The shape of the depressions 265 may conform to the shape of the exterior of the evaporator tubes 210, and the position of the depressions 265 may correspond to the position of the evaporator tubes 210. The rotating portion 220 may therefore be connected to the interface plate 260 by securing the evaporator tubes 210 in the depressions 265 of the interface plate 260.

Heat is transferred through the interface plate 260 from an element to be cooled 270. In various installations of the system 200, there may be a narrow air gap 280 between the interface plate 260 and the element to be cooled 270. In some embodiments, the gap 280 may be filled with a heat conductive material such as oil.

The motive force required to spin the rotating portion 220 may be supplied utilizing any number of driving mechanisms known to those skilled in the art. Examples of suitable driving mechanisms include an electric motor with a drive axis coaxial with the center of the rotating portion 220 and magnetic elements installed in adjacent faces of the rotating 220 and fixed 240 portions of the housing 230.

The rotational speed to accelerate the working fluid may be influenced by any number of factors, including but not limited to the specific geometry of the system 200, the particular working fluid chosen to be used in the system 200, and the ambient conditions. To effectuate the acceleration of the working fluid, the rotating portion 220 may be rotated at 10,000 rpm. Depending on the ambient conditions and the specific characteristics of a given system, the rotational speed of the rotating portion 220 may be more or less than 10,000 rpm.

As the rotating portion spins, axial velocity urges the working fluid to collect at the trailing sides of the evaporator tubes 210. To maintain a proper flow pattern through the evaporator tubes 210, the evaporator tubes 210 may be arced to compensate for the pooling effect of the axial velocity.

The system 200 may be modified according to the requirements of a given installation. The size and number of evaporator tubes 220, the dimensions of the housing 230, use of an interface plate 260 and an air gap 280, may all be adjusted depending on how much heat is being generated by the object to be cooled 270 and the desired operating temperature.

As explained in further detail below, a phase change occurs in the working fluid as the fluid passes through the evaporator tubes 210. The phase change involves a sudden and significant change in volume in the fluid. To accommodate the volume change, a mechanism 290 to compensate for volume change may be provided. The volume change compensation mechanism 290 is installed in fluid communication with the fluid pathway. One volume change compensation mechanism 290 that may be utilized is an expandable bladder.

FIG. 4 illustrates a cross sectional view of an evaporator tube 210. The tube 210 of FIG. 4 includes an inlet 410 and an outlet 420 formed inside the tube body 430. A throat section 440 causes the working fluid to accelerate to a speed equal to or greater than the speed of sound in the working fluid after the working fluid enters the tube 210. The acceleration of the working fluid through the throat section 440 causes a sudden drop in pressure, which may result in cavitation. These factors may assist in the formation of the compression wave in the evaporator tube 210.

The flow of the working fluid through the evaporator tube 210 induces a pressure drop and phase change in the working fluid that results in a lowered temperature, providing the cooling effect of the system 200. The pressure change may span a range of approximately 20 PSI to 100 PSI. In some instances, the pressure may be increased to more than 100 PSI, and in some instance, the pressure may be decreased to less than 20 PSI.

FIG. 5 illustrates a method of operation for the cycle utilized in the cooling systems disclosed herein. A step 510 of the method includes spinning the rotating portion of a housing defining a fluid pathway. In a step 520, the working fluid is introduced at inlets of evaporator tubes in rotating portion of fluid pathway. In a step 530, the fluid accelerates due to the rotation of the rotating portion 220 as the fluid travels through the evaporator tubes 210 to a perimeter of the rotating portion 220. The acceleration of the fluid causes a pressure differential and a phase change in a step 540 that generates the cooling effect. In a step 540, the fluid is shocked as it exits the evaporator tubes.

Critical flow rate, which is the maximum flow rate that can be attained by a compressible fluid as that fluid passes from a high pressure region to a low pressure region (i.e., the critical flow regime), allows for a compression wave to be established and utilized in the critical flow regime in the evaporator tubes 210. Critical flow occurs when the velocity of the fluid is greater than or equal to the speed of sound in the fluid. In critical flow, the pressure in the tube 210 will not be influenced by the exit pressure.

While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. The descriptions are not intended to limit the scope of the invention to the particular forms set forth herein. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments. It should be understood that the above description is illustrative and not restrictive. To the contrary, the present descriptions are intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims and otherwise appreciated by one of ordinary skill in the art. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents. 

1. A cooling method, the method comprising: rotating a portion of a fluid pathway whereby a compressible fluid contained in the pathway is accelerated to a velocity greater than or equal to the speed of sound in the compressible fluid, the acceleration of the compressible fluid establishing a low pressure region in the pathway; forming a compression wave in the compressible fluid as the compressible fluid passes from a high pressure region to the low pressure region as the compressible fluid passes through an evaporator tube; and exchanging heat introduced into the fluid pathway during a phase change of the compressible fluid to extract heat from an element to be cooled.
 2. The method of claim 1, wherein exchanging heat further includes conducting heat through an interface plate in thermal communication with the fluid pathway.
 3. The method of claim 1, wherein exchanging heat further includes exchanging heat through an air gap between the rotating portion of the fluid pathway and the element to be cooled.
 4. The method of claim 3, further comprising increasing the heat transfer rate of the air gap by filling the air gap with oil.
 5. The method of claim 1, wherein rotating a portion of the fluid pathway includes rotating at least one evaporator tube.
 6. The method of claim 5, wherein forming a compression wave further includes initiating cavitation in the evaporator tube to assist in the formation of the compression wave.
 7. The method of claim 1, wherein during the phase change of the compressible fluid, a portion of the compressible fluid is introduced into a volume change compensation mechanism in fluid communication with the fluid pathway to compensate for the volume change associated with the phase change.
 8. The method of claim 1, wherein exchanging heat further includes conducting heat through a solid metal in thermal communication with both the fluid pathway and the element to be cooled.
 9. The method of claim 1, wherein acceleration of the compressible fluid creates a partial vacuum that urges the compressible fluid through the fluid pathway.
 10. The method of claim 1, wherein acceleration of the compressible fluid causes a pressure change that leads to a phase change of the compressible fluid.
 11. The method of claim 10, wherein the pressure change of the compressible fluid occurs within a range of approximately 20 PSI to 100 PSI.
 12. The method of claim 10, wherein the pressure change of the compressible fluid involves a change to an excess of 100 PSI.
 13. The method of claim 10, wherein the pressure change of the compressible fluid involves a change to less than 20 PSI.
 14. A cooling system, the system comprising: an enclosure defining a fluid pathway, at least a portion of the fluid pathway being rotatable about a central axis, the rotatable portion of the fluid pathway including at least one evaporator tube; and a driving mechanism to provide a motive force to drive the rotatable portion of the fluid pathway, wherein fluid in the at least one evaporator tube flows in the critical flow regime to generate a compression wave, the compression wave changing the pressure of the fluid so that the temperature of the fluid is reduced, thereby allowing heat to be exchanged with the fluid in the fluid pathway to remove heat from an element to be cooled.
 15. The system of claim 14, further comprising at least one heat conductive solid in thermal communication with both the fluid pathway and an element to be cooled.
 16. The system of claim 14, further comprising a volume change compensation mechanism in fluid communication with the fluid pathway.
 17. The system of claim 14, further comprising a gap between the rotatable portion and an element to be cooled.
 18. The system of claim 17, wherein the gap is filled with oil to improve heat conductivity.
 19. The system of claim 14, wherein the fluid pathway includes a region in which the fluid undergoes a phase change as the pressure of the fluid changes.
 20. The system of claim 19, wherein the pressure of the fluid changes within a range of approximately 20 PSI to 100 PSI.
 21. The system of claim 19, wherein the pressure of the fluid increases to a pressure greater than 100 PSI.
 22. The system of claim 19, wherein the pressure of the fluid decreases to a pressure less than 20 PSI.
 23. The system of claim 14, wherein the fluid is water. 